WO2020158673A1

WO2020158673A1 - Elastic wave device and multiplexer

Info

Publication number: WO2020158673A1
Application number: PCT/JP2020/002804
Authority: WO
Inventors: 彰道上
Original assignee: 株式会社村田製作所
Priority date: 2019-01-31
Filing date: 2020-01-27
Publication date: 2020-08-06
Also published as: CN113348625A; KR20210091292A; CN113348625B; JPWO2020158673A1; US11936359B2; KR102625090B1; US20220224307A1; JP7168009B2

Abstract

An elastic wave device of the present invention uses SH waves as a main mode and comprises: a substrate (2); an interdigital transducer (IDT) electrode (3) having electrode fingers (4a, 4b) formed on a main surface of the substrate (2); and a protective film (6) which continuously covers the main surface of the substrate (2) and the side surfaces and top surfaces of the electrode fingers (4a, 4b), wherein, from among the portions of the protective film (6) covering the main surface of the substrate (2), a central section between the adjacent electrode fingers (4a, 4b) is thicker than nearby sections near the electrode fingers (4a, 4b).

Description

Acoustic wave devices and multiplexers

The present invention relates to an acoustic wave device, and particularly to an acoustic wave device using SH waves as a main mode and a multiplexer.

Conventionally, a substrate, a comb-shaped electrode provided on the upper surface of the substrate, and a protective film that covers the comb-shaped electrode are provided, and the thickness of the protective film on the upper surface of the electrode fingers forming the comb-shaped electrode and the side surface of the electrode finger. There is disclosed a structure in which the thickness of the protective film is almost equal (for example, Patent Document 1).

In Patent Document 1, considering the moisture resistance as a protective film, its thickness becomes important. That is, it is described that if a certain humidity resistance standard is to be satisfied, it is necessary to secure a certain film thickness even in the thinnest place.

JP, 2006-41589, A

In an acoustic wave device that uses SH waves as a main mode, a Rayleigh wave response occurs at a frequency around 0.75 times that of the main mode. For example, in a multiplexer in which a plurality of filters are commonly connected, if the pass band of the commonly connected partner filter and the frequency of the Rayleigh wave response match, the pass characteristic of the partner filter deteriorates.

Therefore, the present invention provides an elastic wave device capable of changing the frequency at which the Rayleigh wave response is generated without substantially changing the frequency characteristics of the main mode.

In order to achieve the above object, an acoustic wave device according to an aspect of the present invention is an acoustic wave device that uses SH waves as a main mode, and includes a substrate and a plurality of substrates formed on a main surface of the substrate. An IDT electrode having electrode fingers; and a protective film that seamlessly covers the main surface of the substrate, the side surfaces and the upper surfaces of the plurality of electrode fingers, among the portions of the protective film that cover the main surface of the substrate. An intermediate portion between the adjacent electrode fingers is thicker than a portion near the electrode fingers.

By doing this, by providing the protective film with a non-uniform thickness, it is possible to change the frequency at which the Rayleigh wave response is generated, compared to the case where the protective film has a uniform thickness. At this time, unless the design parameter of the IDT electrode is changed, the frequency characteristic of the main mode does not substantially change. Therefore, it is possible to obtain the acoustic wave device capable of changing the frequency at which the Rayleigh wave response is generated without substantially changing the frequency characteristics of the main mode.

For example, when the Rayleigh wave response adversely affects the pass characteristics of other filters, by providing a protective film with a non-uniform thickness, the frequency characteristics of the Rayleigh wave response can be changed by other filters while maintaining the frequency characteristics of the main mode. Can be shifted from the pass band of.

FIG. 1 is a plan view schematically showing an example of a general structure of a SAW resonator. FIG. 2 is a sectional view schematically showing an example of a general structure of a SAW resonator. FIG. 3 is a cross-sectional view showing the shape of the protective film according to Reference Example 1. FIG. 4 is a cross-sectional view showing the shape of the protective film according to the first embodiment. FIG. 5 is a graph showing the frequency characteristics of the SAW resonators according to Reference Example 1 and Example 1. FIG. 6 is a graph showing the frequency characteristics of the SAW resonators according to Reference Example 1 and Example 1. FIG. 7 is a cross-sectional view showing the shape of the protective film according to Reference Example 2. FIG. 8 is a cross-sectional view showing the shape of the protective film according to the second embodiment. FIG. 9 is a cross-sectional view showing the shape of the protective film according to the third embodiment. FIG. 10 is a sectional view showing the shape of the protective film according to the fourth embodiment. FIG. 11 is a sectional view showing the shape of the protective film according to the fifth embodiment. FIG. 12 is a cross-sectional view showing the shape of the protective film according to Example 6. FIG. 13 is a graph showing frequency characteristics of SAW resonators according to Reference Example 2 and Examples 2 to 6. FIG. 14 is a functional block diagram showing an example of a general configuration of a multiplexer.

Embodiments of the present invention will be described in detail with reference to examples and drawings. It should be noted that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection forms, and the like shown in the following embodiments are examples, and are not intended to limit the present invention.

Before describing the acoustic wave device according to the embodiment, a general structure of the acoustic wave device will be described below by taking an example of a surface acoustic wave (SAW: Surface Acoustic Wave) resonator.

FIG. 1 is a plan view schematically showing an example of a general structure of a SAW resonator (hereinafter, also simply referred to as a resonator). As shown in FIG. 1, the resonator 1 includes a substrate 2 and a pair of comb-teeth-

shaped electrodes

3 a and 3 b arranged on the substrate 2. The pair of comb-teeth-

shaped electrodes

3 a and 3 b form the IDT electrode 3.

The comb-teeth-shaped electrode 3a is arranged in a comb-teeth shape and is composed of a plurality of electrode fingers 4a that are parallel to each other and a bus bar electrode 5a that connects the respective one ends of the plurality of electrode fingers 4a. The comb-teeth-shaped electrode 3b is arranged in a comb-teeth shape and includes a plurality of electrode fingers 4b parallel to each other and a bus bar electrode 5b connecting one end of each of the plurality of electrode fingers 4b. The plurality of

electrode fingers

4a and 4b are formed so as to extend in a direction orthogonal to the elastic wave propagation direction X.

The resonator 1 shown in FIG. 1 is for explaining a general structure of a SAW resonator, and includes the number and length of the

electrode fingers

4a and 4b forming the comb-

shaped electrodes

3a and 3b. Sa, etc. are not limited to this.

FIG. 2 is a sectional view schematically showing an example of a general structure of a SAW resonator, and corresponds to the section taken along the line II-II in FIG. As shown in FIG. 2, the substrate 2 is composed of a laminated body including a piezoelectric layer 23, a low acoustic velocity film 22, and a high acoustic velocity support substrate 21. The IDT electrode 3 (that is, the

electrode fingers

4a and 4b and the

bus bar electrodes

5a and 5b) is composed of a laminated body including an adhesion layer 31, a main electrode layer 32, and an adhesion layer 33.

The substrate 2 is composed of a laminated body in which a high acoustic velocity support substrate 21, a low acoustic velocity film 22, and a piezoelectric layer 23 are laminated in this order.

The high sound velocity support substrate 21 is a substrate that supports the low sound velocity film 22, the piezoelectric layer 23, the IDT electrode 3, and the protective film 6. The high acoustic velocity support substrate 21 is a substrate in which the acoustic velocity of the bulk wave in the high acoustic velocity support substrate 21 is higher than the acoustic velocity of the elastic wave (surface wave) propagating in the piezoelectric layer 23, and is made of, for example, Si (silicon). Composed. The thickness of the high sound velocity support substrate 21 is not particularly limited.

The low acoustic velocity film 22 is a film in which the acoustic velocity of the bulk wave in the low acoustic velocity film 22 is slower than the acoustic velocity of the elastic wave propagating in the piezoelectric layer 23, and is composed of, for example, SiO 2 (silicon dioxide) as a main component. Composed of materials. The thickness of the low acoustic velocity film 22 is, for example, 673 nm.

The piezoelectric layer 23 is a layer in which a surface acoustic wave excited by the IDT electrode 3 propagates, and is, for example, 50° Y-cut X-propagating LiTaO3 piezoelectric single crystal or piezoelectric ceramic (50° from the Y axis with the X axis as the central axis). It is composed of a lithium tantalate single crystal or ceramics cut along a plane whose normal is the rotated axis. The thickness of the piezoelectric layer 23 is, for example, 600 nm.

According to the substrate 2 having the above-described laminated structure, the efficiency of confining elastic wave energy in the thickness direction of the substrate 2 is increased, so that the Q value at the resonance frequency and the anti-resonance frequency can be increased. However, it is not essential that the substrate 2 has a laminated structure, and the substrate 2 may be configured by a single-layer piezoelectric substrate.

The IDT electrode 3 is formed on the substrate 2 and is composed of a laminated body including an adhesion layer 31, a main electrode layer 32, and an adhesion layer 33. The laminated structure of the IDT electrode 3 shown in FIG. 2 is applied to the

electrode fingers

4a and 4b and the

bus bar electrodes

5a and 5b.

The adhesion layer 31 is a layer for improving the adhesion between the piezoelectric layer 23 and the main electrode layer 32, and is made of, for example, Ti (titanium). The adhesion layer 31 has a thickness of 6 nm, for example.

The main electrode layer 32 is made of, for example, Al (aluminum) or an Al alloy. The thickness of the main electrode layer 32 is, for example, 130 nm.

The adhesion layer 33 is a layer for improving the adhesion between the main electrode layer 32 and the protective film 6, and is made of, for example, Ti (titanium). The adhesion layer 33 has a thickness of 12 nm, for example.

The line width w of the IDT electrode 3 (particularly the

electrode fingers

4a and 4b) is 0.5 μm, and the arrangement interval L is 1 μm. The arrangement interval L corresponds to half of 2.0 μm, which is the wavelength λ of the surface acoustic wave propagating through the piezoelectric layer 23.

The protective film 6 is a layer that improves the durability of the IDT electrode 3, and is made of, for example, a material whose main component is SiO 2 (silicon dioxide). The protective film 6 seamlessly covers the main surface of the substrate 2 on which the IDT electrode 3 is formed, and the side surface and the upper surface of the IDT electrode 3.

The resonator 1 configured as described above is an example of an acoustic wave device that uses SH waves as a main mode, and a Rayleigh wave response occurs at a frequency around 0.75 times that of the main mode.

The resonator 1 can be used, for example, for a plurality of filters that are commonly connected to form a multiplexer. At this time, if the pass band of the commonly-connected filter on the other side and the frequency of the Rayleigh wave response match, the pass characteristic of the filter on the other side deteriorates. Therefore, it becomes necessary to shift the frequency of the Rayleigh wave response from the pass band of the commonly connected counterpart filter.

For example, the frequency of the Rayleigh wave response can be changed by changing the design parameters of the IDT electrode 3 (the line width w, the arrangement interval L described above, etc.), but in this case, the frequency characteristic of the main mode also changes. Therefore, it is not effective as a practical measure.

Therefore, the present inventors have conceived a structure in which the film thickness of the protective film is provided unevenly by paying attention to the design parameter on which the Rayleigh wave depends, among SH waves and Rayleigh waves. Hereinafter, the characteristics of the film thickness of the protective film in the resonator according to the embodiment will be described in detail. In the following description, the

electrode fingers

4a and 4b are collectively referred to as the electrode finger 4.

(Embodiment)
FIG. 3 is a cross-sectional view showing the shape of the protective film 6 according to Reference Example 1. In FIG. 3, the range from the electrode finger 4 to the midpoint between each electrode finger (not shown) adjacent to both sides of the electrode finger 4 is shown with one electrode finger 4 of the IDT electrode 3 as the center. .. A resonator having the protective film 6 having the shape shown in FIG. 3 is referred to as a resonator 70.

In the resonator 70, the first portion of the protective film 6 covering the main surface of the substrate 2 has a uniform thickness of 30 nm, and the second portion of the protective film 6 covering the upper surfaces of the electrode fingers 4 has a uniform thickness of 50 nm. The thickness of the third portion of the protective film 6 covering the side surface of the electrode finger 4 is 50 nm and uniform. The cross-sectional structure shown in FIG. 3 is provided centering on each electrode finger 4 in the resonator 70.

FIG. 4 is a cross-sectional view showing the shape of the protective film 6 according to the first embodiment. FIG. 4A shows a range from one electrode finger 4 of the IDT electrode 3 as a center to an intermediate point between the electrode finger 4 and each of electrode fingers (not shown) adjacent to both sides of the electrode finger 4. It is shown. In FIG. 4B, two

adjacent electrode fingers

4a and 4b are shown. The "adjacent electrode fingers" are the electrode fingers 4a and the electrode fingers 4b arranged adjacent to each other, and the adjacent electrode fingers 4a among the plurality of electrode fingers 4a and the plurality of electrode fingers 4b. It does not mean the adjacent electrode fingers 4b among them. A resonator having the protective film 6 having the shape shown in FIG. 4 will be referred to as a resonator 71.

In the resonator 71, in the first portion of the protective film 6 that covers the main surface of the substrate 2, the thickness of the intermediate portion between the adjacent electrode fingers 4 is 50 nm, and the thickness in the vicinity of the electrode fingers 4 is 10 nm. .. Further, the thickness of the second portion of the protective film 6 covering the upper surface of the electrode finger 4 is 50 nm and uniform, and the thickness of the third portion of the protective film 6 covering the side surface of the electrode finger 4 is uniform 50 nm. That is, in the resonator 71, the intermediate portion between the adjacent electrode fingers 4 in the first portion of the protective film 6 covering the main surface of the substrate 2 is thicker than the portion in the vicinity of the electrode fingers 4. For example, when the gap (gap) between the two protective layers 6 covering the side surfaces of the

electrode fingers

4a and 4b and facing each other is G, the intermediate portion between the adjacent electrode fingers is the intermediate portion of the two protective layers 6 described above. It is a range that includes points and is separated by 0 G or more and 0.1 G or less on the electrode finger 4a side and the electrode finger 4b side with respect to the midpoint. Further, the vicinity of the electrode finger is separated from the protective layer 6 covering the side surface of the electrode finger 4a by 0 G or more and 0.1 G or less, or separated from the protective layer 6 covering the side surface of the electrode finger 4b by 0 G or more and 0.1 G or less. It is a range. The cross-sectional structure shown in FIG. 4 is provided centering on each electrode finger 4 in the resonator 71.

The models of the

resonators

70 and 71 were set according to the dimensional conditions shown in FIGS. 3 and 4, and the frequency characteristics of impedance were obtained by simulation. The design parameters of the IDT electrode 3 are the same for the

resonators

70 and 71.

FIG. 5 is a graph showing an example of frequency characteristics of impedance of the

resonators

70 and 71. As can be seen in FIG. 5, the response of the main mode occurring in the vicinity of 1900 MHz to 2000 MHz is almost the same in the

resonators

70 and 71. That is, it can be seen that whether the protective film 6 is made uniform or not does not substantially affect the frequency characteristics of the main mode. On the other hand, it can be seen that there is a difference between the

resonators

70 and 71 in the frequency of the Rayleigh wave response generated near 1420 MHz to 1440 MHz.

FIG. 6 is a graph showing an enlarged Rayleigh wave response. As shown in FIG. 6, the frequencies of the Rayleigh wave response are about 5 MHz in the

resonators

70 and 71.

From this result, it is possible to change the frequency at which the Rayleigh wave response is generated by providing the protective film with a non-uniform thickness without substantially changing the frequency characteristics of the main mode as compared with the case where the thickness of the protective film is uniform. You can see that.

In the following, resonators according to other examples in which the shape of the protective film 6 is different will be described.

FIG. 7 is a cross-sectional view showing the shape of the protective film 6 according to Reference Example 2. In FIG. 7, a range from the electrode finger 4 of the IDT electrode 3 to an intermediate point between the electrode finger 4 and each of the electrode fingers (not shown) adjacent to both sides of the electrode finger 4 is shown. .. A resonator having the protective film 6 having the shape shown in FIG. 7 is referred to as a resonator 80.

In the resonator 80, the first portion of the protective film 6 covering the main surface of the substrate 2 has a uniform thickness of 30 nm, and the second portion of the protective film 6 covering the upper surfaces of the electrode fingers 4 has a uniform thickness of 30 nm. The thickness of the third portion of the protective film 6 that covers the side surface of the electrode finger 4 is uniform at 30 nm. The cross-sectional structure shown in FIG. 7 is provided centering on each electrode finger 4 in the resonator 80.

FIG. 8 is a sectional view showing the shape of the protective film 6 according to the second embodiment. FIG. 8 shows a range from the electrode finger 4 of the IDT electrode 3 as a center to an intermediate point between the electrode finger 4 and each of the electrode fingers (not shown) adjacent to both sides of the electrode finger 4. .. A resonator having the protective film 6 having the shape shown in FIG. 8 will be referred to as a resonator 81.

In the resonator 81, in the first portion of the protective film 6 that covers the main surface of the substrate 2, the thickness of the intermediate portion between the adjacent electrode fingers 4 is 50 nm, and the thickness in the vicinity of the electrode fingers 4 is 10 nm. .. Further, of the second portion of the protective film 6 covering the upper surface of the electrode finger 4, the thickness of the portion covering the central portion of the upper surface is 50 nm, and the thickness of the portion covering the end portion of the upper surface is 10 nm. In addition, the thickness of the third portion of the protective film 6 that covers the side surface of the electrode finger 4 is uniform at 30 nm. That is, in the resonator 81, in the first portion of the protective film 6 that covers the main surface of the substrate 2, the intermediate portion between the adjacent electrode fingers 4 is thicker than the neighboring portion of the electrode finger 4, and Of the second portion of the protective film 6 covering the upper surface of 4, the portion covering the central portion of the upper surface is thicker than the portion covering the end portion of the upper surface. The cross-sectional structure shown in FIG. 8 is provided centering on each electrode finger 4 in the resonator 81.

FIG. 9 is a sectional view showing the shape of the protective film 6 according to the third embodiment. In FIG. 9, a range from the electrode finger 4 of the IDT electrode 3 to an intermediate point between the electrode fingers 4 and the electrode fingers (not shown) adjacent to both sides of the electrode finger 4 is shown. .. A resonator having the protective film 6 having the shape shown in FIG. 9 will be referred to as a resonator 82.

In the resonator 82, in the first portion of the protective film 6 that covers the main surface of the substrate 2, the thickness of the intermediate portion between the adjacent electrode fingers 4 is 50 nm, and the thickness in the vicinity of the electrode fingers 4 is 10 nm. .. Further, of the second portion of the protective film 6 covering the upper surface of the electrode finger 4, the thickness of the portion covering the central portion of the upper surface is 10 nm, and the thickness of the portion covering the end portion of the upper surface is 50 nm. In addition, the thickness of the third portion of the protective film 6 that covers the side surface of the electrode finger 4 is uniform at 30 nm. That is, in the resonator 82, in the first portion of the protective film 6 that covers the main surface of the substrate 2, the intermediate portion between the adjacent electrode fingers 4 is thicker than the vicinity of the electrode finger 4, and Of the second portion of the protective film 6 that covers the upper surface of 4, the portion that covers the central portion of the upper surface is thinner than the portion that covers the end portion of the upper surface. The sectional structure shown in FIG. 9 is provided centering on each electrode finger 4 in the resonator 82.

FIG. 10 is a sectional view showing the shape of the protective film 6 according to the fourth embodiment. FIG. 10 shows a range from the electrode finger 4 of the IDT electrode 3 as a center to a middle point between the electrode finger 4 and each of the electrode fingers (not shown) adjacent to both sides of the electrode finger 4. .. A resonator having the protective film 6 having the shape shown in FIG. 10 will be referred to as a resonator 83.

In the resonator 83, in the first portion of the protective film 6 covering the main surface of the substrate 2, the thickness of the intermediate portion between the adjacent electrode fingers 4 is 50 nm, and the thickness in the vicinity of the electrode fingers 4 is 10 nm. .. Further, the thickness of the second portion of the protective film 6 covering the upper surface of the electrode finger 4 is 30 nm and uniform. Further, of the third portion of the protective film 6 that covers the side surface of the electrode finger 4, the thickness of the portion that covers the lower portion of the side surface is 50 nm, and the thickness of the portion that covers the upper portion of the side surface is 10 nm. That is, in the resonator 83, in the first portion of the protective film 6 that covers the main surface of the substrate 2, the intermediate portion between the adjacent electrode fingers 4 is thicker than the neighboring portion of the electrode finger 4, and Of the third portion of the protective film 6 that covers the side surface of 4, the portion that covers the lower portion of the side surface is thicker than the portion that covers the upper portion of the side surface. The cross-sectional structure shown in FIG. 10 is provided centering on each electrode finger 4 in the resonator 83.

FIG. 11 is a sectional view showing the shape of the protective film 6 according to the fifth embodiment. In FIG. 11, a range from the electrode finger 4 of the IDT electrode 3 to an intermediate point between the electrode finger 4 and each of the electrode fingers (not shown) adjacent to both sides of the electrode finger 4 is shown. .. A resonator having the protective film 6 having the shape shown in FIG. 11 is referred to as a resonator 84.

In the resonator 84, in the first portion of the protective film 6 that covers the main surface of the substrate 2, the thickness of the intermediate portion between the adjacent electrode fingers 4 is 50 nm, and the thickness in the vicinity of the electrode fingers 4 is 10 nm. .. Further, the thickness of the second portion of the protective film 6 covering the upper surface of the electrode finger 4 is 30 nm and uniform. Further, of the third portion of the protective film 6 that covers the side surface of the electrode finger 4, the thickness of the portion that covers the lower portion of the side surface is 10 nm, and the thickness of the portion that covers the upper portion of the side surface is 50 nm. That is, in the resonator 84, in the first portion of the protective film 6 that covers the main surface of the substrate 2, the intermediate portion between the adjacent electrode fingers 4 is thicker than the vicinity of the electrode finger 4, and Of the third portion of the protective film 6 that covers the side surface of 4, the portion that covers the lower portion of the side surface is thinner than the portion that covers the upper portion of the side surface. The cross-sectional structure shown in FIG. 11 is provided centering on each electrode finger 4 in the resonator 84.

FIG. 12 is a sectional view showing the shape of the protective film 6 according to the sixth embodiment. In FIG. 12, a range from the electrode finger 4 of the IDT electrode 3 to the middle point between the electrode finger 4 and each of the electrode fingers (not shown) adjacent to both sides of the electrode finger 4 is shown. .. A resonator having the protective film 6 having the shape shown in FIG. 12 is referred to as a resonator 85.

In the resonator 85, the thickness of the intermediate portion between the adjacent electrode fingers 4 of the first portion of the protective film 6 covering the main surface of the substrate 2 is 50 nm, and the thickness in the vicinity of the electrode fingers 4 is 10 nm. .. Further, of the second portion of the protective film 6 covering the upper surface of the electrode finger 4, the thickness of the portion covering the central portion of the upper surface is 50 nm, and the thickness of the portion covering the end portion of the upper surface is 10 nm. Further, of the third portion of the protective film 6 that covers the side surface of the electrode finger 4, the thickness of the portion that covers the lower portion of the side surface is 50 nm, and the thickness of the portion that covers the upper portion of the side surface is 10 nm. That is, in the resonator 83, in the first portion of the protective film 6 that covers the main surface of the substrate 2, the intermediate portion between the adjacent electrode fingers 4 is thicker than the neighboring portion of the electrode finger 4, and Of the second portion of the protective film 6 covering the upper surface of 4, the portion covering the central portion of the upper surface is thicker than the portion covering the end portion of the upper surface. Furthermore, of the third portion of the protective film 6 that covers the side surface of the electrode finger 4, the portion that covers the lower portion of the side surface is thicker than the portion that covers the upper portion of the side surface. The sectional structure shown in FIG. 12 is provided centering on each electrode finger 4 in the resonator 85.

The models of the resonators 80 to 85 were set according to the dimensional conditions shown in FIGS. 7 to 12, and the impedance frequency characteristics were obtained by simulation. The design parameters of the IDT electrode 3 were the same for the resonators 80 to 85. The response of the main mode was almost the same in the resonators 80 to 85 (not shown).

FIG. 13 is a graph showing an enlarged Rayleigh wave response of the resonators 80 to 85. As shown in FIG. 13, the frequency of the Rayleigh wave response differs by about 3 MHz to 9 MHz between the resonator 80 and each of the resonators 81 to 85.

The above-described resonator provided with the protective film having a non-uniform thickness can be used, for example, for a plurality of filters that are commonly connected and that form a multiplexer.

FIG. 14 is a functional block diagram showing an example of a general configuration of a multiplexer. As shown in FIG. 14, the multiplexer 90 includes

filters

91 and 92 whose one ends are commonly connected to each other. At least one of the

filters

91 and 92 has an elastic wave device in which a protective film has a nonuniform thickness ( For example, the resonator 71, any one of the resonators 81 to 85 is used.

In the multiplexer 90, for example, it is assumed that the frequency of the Rayleigh wave response of the filter 91 matches the pass band of the filter 92. In this case, by configuring the filter 91 with a resonator in which the thickness of the protective film is not uniform, it is possible to shift the frequency of the Rayleigh wave response of the filter 91 from the pass band of the filter 92 while maintaining the pass characteristic of the filter 91. it can.

The elastic wave device and the multiplexer according to the embodiments of the present invention have been described above based on the embodiments, but the present invention is not limited to the individual embodiments. As long as it does not depart from the gist of the present invention, various modifications made by those skilled in the art may be applied to the present embodiment, or a configuration constructed by combining components in different embodiments may be one or more of the present invention. It may be included in the range of the aspect.

The method for forming the protective film having a non-uniform thickness is not particularly limited, but as an example, the protective film may be formed by the sputtering conditions when forming the protective film or the etching and milling conditions in the step of adjusting the frequency by scraping the protective film. You can That is, the protective film having a non-uniform thickness can be formed at a low cost by utilizing a plurality of existing processes.

Specifically, the processing of the protective film into a specific shape is performed at the same time as adjusting the frequency of the main mode after checking the waveform before frequency adjustment by controlling during frequency adjustment (when cutting the protective film). May be.

Also, before forming the protective film and before adjusting the frequency, the position of the main mode and the Rayleigh wave response can be grasped, and an adaptive method can be adopted by changing the conditions of sputtering, etching, and milling for each sample if necessary. it can.

(Summary)
As described above, an acoustic wave device according to an aspect of the present invention is an acoustic wave device that uses SH waves as a main mode, and includes a substrate and a plurality of electrode fingers formed on the main surface of the substrate. An IDT electrode having: and a protective film that seamlessly covers the main surface of the substrate, side surfaces and upper surfaces of the plurality of electrode fingers, and is adjacent to a part of the protective film that covers the main surface of the substrate. The middle portion of the electrode finger is thicker than the vicinity of the electrode finger.

Also, of the portion of the protective film that covers the upper surface of the electrode finger, the portion that covers the central portion of the upper surface may be thicker than the portion that covers the end portion of the upper surface.

Further, of the portion of the protective film that covers the upper surface of the electrode finger, the portion that covers the central portion of the upper surface may be thinner than the portion that covers the end portion of the upper surface.

Also, of the portion of the protective film that covers the side surface of the electrode finger, the portion that covers the lower portion of the side surface may be thicker than the portion that covers the upper portion of the side surface.

Also, of the portion of the protective film that covers the side surface of the electrode finger, the portion that covers the lower portion of the side surface may be thinner than the portion that covers the upper portion of the side surface.

The substrate may be composed of a piezoelectric material containing lithium tantalate, and the IDT electrode may be composed of a piezoelectric layer formed on one main surface.

Further, the substrate is made of a piezoelectric material containing lithium tantalate, the piezoelectric layer having the IDT electrode formed on one main surface, and the acoustic wave velocity propagating through the piezoelectric layer rather than the acoustic wave velocity propagating through the piezoelectric layer. A bulk acoustic wave velocity is higher than that of a high acoustic velocity supporting substrate having a high bulk acoustic velocity and a high acoustic velocity supporting substrate and the piezoelectric layer. And a low sonic film that is slow.

As a result, regardless of whether the substrate is an acoustic wave device having a single-layer structure or a laminated structure, the frequency at which the Rayleigh wave response is generated can be changed without substantially changing the frequency characteristics of the main mode. Wave device is obtained.

The maximum thickness of the protective film may be half the thickness of the IDT electrode or less.

This will prevent the Q value from deteriorating when the protective film is thick because the protective film is too thick. As a result, an elastic wave device having excellent characteristics can be obtained.

The multiplexer according to an aspect of the present invention includes a plurality of filters whose one ends are connected to each other, and at least one filter among the plurality of filters is configured using the acoustic wave device.

∙ This makes it possible to obtain a multiplexer with excellent pass characteristics based on the effects of the acoustic wave device described above.

The present invention can be widely used for communication devices such as mobile phones as an elastic wave device and a multiplexer using the elastic wave device.

1, 70, 71, 80 to 85 Resonator 2 Substrate 3

IDT electrodes

3a, 3b Comb-shaped

electrodes

4, 4a,

4b Electrode fingers

5a, 5b Busbar electrode 6 Protective film 21 High acoustic velocity support substrate 22 Low acoustic velocity film 23

Piezoelectric body Layer

31, 33 Adhesion layer 32 Main electrode layer 90

Multiplexer

91, 92 Filter

Claims

An acoustic wave device that uses SH waves as a main mode is
Board,
An IDT (InterDigital Transducer) electrode having a plurality of electrode fingers formed on the main surface of the substrate;
A protective film that seamlessly covers the main surface of the substrate, side surfaces and upper surfaces of the plurality of electrode fingers;
Equipped with
Of the portion of the protective film that covers the main surface of the substrate, an intermediate portion between adjacent electrode fingers is thicker than a portion near the electrode fingers,
Acoustic wave device.
Of the portion of the protective film that covers the upper surface of the electrode finger, the portion that covers the central portion of the upper surface is thicker than the portion that covers the end portion of the upper surface,
The acoustic wave device according to claim 1.
Of the portion of the protective film that covers the upper surface of the electrode finger, the portion that covers the central portion of the upper surface is thinner than the portion that covers the end portion of the upper surface,
The acoustic wave device according to claim 1.
Of the portion of the protective film that covers the side surface of the electrode finger, the portion that covers the lower portion of the side surface is thicker than the portion that covers the upper portion of the side surface,
The acoustic wave device according to any one of claims 1 to 3.
Of the portion of the protective film that covers the side surface of the electrode finger, the portion that covers the lower portion of the side surface is thinner than the portion that covers the upper portion of the side surface,
The acoustic wave device according to any one of claims 1 to 3.
The substrate is composed of a piezoelectric material containing lithium tantalate, and the IDT electrode is composed of a piezoelectric layer formed on one main surface.
The acoustic wave device according to any one of claims 1 to 5.
The substrate is
A piezoelectric layer composed of a piezoelectric material containing lithium tantalate, wherein the IDT electrode is formed on one main surface;
A higher acoustic velocity support substrate in which the acoustic velocity of a bulk wave propagating is higher than the acoustic velocity of an acoustic wave propagating in the piezoelectric layer,
A low sonic film that is disposed between the high acoustic velocity support substrate and the piezoelectric layer, and has a low bulk acoustic wave velocity that propagates as compared to the acoustic wave acoustic velocity that propagates through the piezoelectric layer.
The acoustic wave device according to any one of claims 1 to 5.
The maximum thickness of the protective film is less than half the thickness of the IDT electrode,
The acoustic wave device according to any one of claims 1 to 7.
Equipped with multiple filters with one end connected to each other,
At least one filter of the plurality of filters is configured using the acoustic wave device according to any one of claims 1 to 8,
Multiplexer.